The greenbug, Schizaphis graminum (Rondani), is a major pest of cereals in some parts of the world and is of particular concern because it can be resistant to some insecticides and overcome the resistance of crops. In the UK, it has never been found on crops, but two rather little-known and closely-related species (Schizaphis holci and Schizaphis agrostis) are associated with the wild grasses, Holcus lanatus and Agrostis stolonifera. Since 1987, winged (alate) aphids morphologically resembling the greenbug have been found in increasing numbers in 12.2 m high suction-trap samples of the Rothamsted Insect Survey (RIS); hence, studies were undertaken to establish their identity. Clones (=asexual lineages) established from populations collected from H. lanatus in southern England showed strong preference for Holcus over Agrostis and Hordeum in laboratory tests and produced sexual morphs when transferred to short-day conditions, the males being apterous, as expected for S. holci. Multivariate morphometric comparisons of alatae caught in UK RIS suction traps in 2007 and 2011 with named specimens from museum collections, including S. graminum from many countries, indicated that the suction-trapped alatae were mostly S. agrostis and S. holci. Cytochrome c oxidase subunit I (COI) mtDNA obtained from 62 UK specimens from suction-traps had 95.4–100% sequence identity with US specimens of S. graminum. Two of the UK specimens had identical COI sequence to the US sorghum-adapted form of S. graminum, and these specimens also had 100% identity with a 640 bp fragment of nDNA CytC, indicating that this form of S. graminum may already be present in the UK. Present and future economic implications of these results are discussed.

Insect pests are major yield reducers in sorghum under traditional farming practices in Africa. The use of resistant varieties in an integrated pest management scheme provides the most cost effective and practical means of sorghum insect control. Corneous grain sorghums are more weevil resistant than their softer endosperm counterparts. A wide range of sources of resistance to shootfiy, stem-borer and greenbug are known. Breeding for resistance to sorghum insects has been practised with varying degrees of success. Greenbug resistance breeding in sorghum has been successful in the U.S.A. Stem-borers are perhaps the most serious group of sorghum insects in Eastern Africa and further efforts are needed in breeding for resistance to these pests. In an effective pest resistance breeding work, the breeder and the entomologist must work as a team to make the fastest possible progress. Where several pests are of concern in an area, genotypes with multiple resistance in good agronomic backgrounds are needed.